I've had a few sporadic reports of people having problems on NetWare 
3.12; almost all of them are the result of using the in-place upgrade 
from NetWare 3.11, which appears to be a disaster waiting to happen...

Here are some things to check or try:

1:  If you have upgraded to the VLM shells, then you probably have the
    statement "LASTDRIVE=Z" in your CONFIG.SYS file - this will prevent
    all versions of Pegasus Mail from functioning correctly. You can
    fix this in one of two ways: either by setting LASTDRIVE to some
    value lower than Z (the VLM shells don't really seem to need the
    setting in any case), or by creating a DOS environment variable
    called PMDRIVE which points to a drive letter already mapped to
    the SYS: volume of your server - for example
    
          SET PMDRIVE=L

Reason: The VLM shells are radically different from previous shell 
versions and function differently in a number of critical ways, one of 
which is drive reporting to NetWare-aware applications. The next releases 
of Pegasus Mail and WinPMail will work around this.

2:  Make sure you have at least one free, unmapped drive letter, or
    a PMDRIVE variable as described above.

Reason: Pegasus Mail has to create a mapping to your SYS: volume in order 
to operate, but current versions will fail quietly if a letter is not 
available. The next releases will issue a warning when this happens.

3:  Make sure that group EVERYONE has [C] rights in SYS:MAIL.
4:  If EVERYONE appears to have [C] rights in SYS:MAIL and you have
    done the in-place upgrade, remove the grant using REMOVE, then
    grant it again using GRANT.

Reason: the in-place upgrade sometimes seems to leave group rights 
assignments in an unpredictable state.

5:  If you have upgraded from a system where the user was already
    running WinPMail, try deleting the file WINPMAIL.PRO in the user's
    directory in SYS:MAIL.

Reason: the in-place upgrade sometimes appears to change the bindery ID 
of users while upgrading, which can invalidate the Pegasus Mail 
preference file.